Fundamentals of light

The color of sun is the purest color.

Luminous flux:-The amount of light immersing from the source.

                           Unit:-lumen (lm) and

                            symbol is Φ

Luminous Intensity:- The amount of light immersing from the source and falling on a surface per unit area at a point.

                                    Unit:- Candela (Cd)

                                   1 ft Candela = 10 Cd

Illuminance:- The amount of light received by eye per unit area.

                         E= dΦ/dA

                         Unit:-lux –Cd/m²

Luminance:- The amount of light received by eye per unit apparent area.

Apparent Area (A) = |Acosθ|

Unit:- Cd/m²

 Laws of illuminance:-

1). Cosine law:-

                 E=I Cosθ/d²

2). Luminance low:-

                 E=I/d²

Where d is distance from the source to the eye.

Types of visions:-

There are three types of visions

1). Photopic

2). Mesopic

3). Scotopic

1. Photopic:-  It is the day light vision in which cones are more active then rods.

i.e. (Cones↑ Rods↓)

*Rods= 5 to 6 times of Cones

*Retina= Rods + Cones

When Rods are active then we only able to fell the appearance of the object, and when the cones are active then only we are able to see the object clearly.

2. Mesopic:-  It is the evening time vision when sun is about to set. At that time cones and rods both are equally active.

i.e. (Cones = Rods)

3. Scotopic:- It is the night vision in which cones are less active then rods.

i.e. (Cones↓ Rods↑)